The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems for performing deposition and/or etching typically include a processing chamber with a pedestal. A substrate such as a semiconductor wafer may be arranged on the pedestal. For example in a chemical vapor deposition (CVD) process, a gas mixture including one or more precursors may be introduced into the processing chamber to deposit film on the substrate or to etch the substrate. In some substrate processing systems, plasma may be used to activate chemical reactions and is referred to herein as plasma enhanced CVD (PECVD).
Amorphous carbon film may be used as a hardmask or etch stop layer during semiconductor processing. The amorphous carbon film is known as an ashable hardmask (AHM) film because the film may be removed by ashing. As aspect ratios in lithography increase, AHMs require higher etch selectivity. Current methods of forming highly selective AHMs using PECVD processes produce AHMs with varying stresses and etch selectivity.
The amorphous carbon film typically has hydrocarbon or polymer content. The carbon-hydrogen content facilitates opening the hardmask while making the film less selective to dielectric etch chemistries. In 3-D memory applications, the hardmask film should be highly selective. As a result, the carbon-hydrogen content of the film should be reduced without reducing the carbon-carbon content. This poses a challenge of depositing a film that strikes a balance between being able to be removed during the hardmask opening process and being sufficiently selective during the dielectric etching processes.